This invention relates to a liquid crystal display apparatus, liquid crystal device and liquid crystal display system with which a recorded picture having the stereoscopic information may be viewed as a three-dimensional picture, or a so-called stereo image, using a liquid crystal display. More particularly, it relates to a liquid crystal display apparatus, a liquid crystal device and a liquid crystal display system so designed that, even if the position of a viewer""s head is varied, the stereo image can be appreciated satisfactorily.
Up to now, various techniques of representing an image three-dimensionally were developed, and the representing methods for three-dimensional images were researched and put to use in many fields, such as photography, cinema or television. The methods for demonstrating a three-dimensional image may be classified into a method employing glasses and a method not employing them.
Typical of the system employing glasses are an anaglyphic system in which a viewer wears so-called red glasses or blue glasses, and a system in which a viewer wears polarizing glasses. With these systems, an image presenting parallax is input to left and right eyes of a user whereby the viewer may see the image as a stereo image.
On the other hand, a 3D (three-dimensional) display apparatus of the lenticular system or the parallax barrier system is already in the stage of practical application. With these systems, an area that permits stereo vision is extremely narrow in the transverse direction and is xc2x1several cm, so that limitations are perpetually imposed on user head positions.
So, such a back light splitting system, disclosed in the Japanese Laying-Open Patent Publication H-10-63199, has been proposed as a liquid crystal apparatus in which the stereo image is not impaired even if the user viewing position is slightly offset in the left and right directions with respect to a liquid crystal display screen, and in which the stereo image can be appreciated as the horizontal resolution proper to the liquid crystal display screen is maintained.
The back light splitting system is hereinafter explained. A back light of a routine liquid crystal device is arranged at back of the liquid crystal panel with planar illumination, having an equivalent area to the panel area, in intimate contact with the liquid crystal panel, so that non-directive light is incident on the user""s left and right eyes. In the back light splitting system, as contrasted to this conventional system, two back lights, having an appreciably smaller area than a liquid crystal panel, are separately arranged for left and right eyes at the positions spaced apart from the liquid crystal panel a distance slightly larger than the focal length of a convex lens, having a diameter approximately equal to that of the liquid crystal display screen, to take advantage of the directivity of the convex lens.
FIG. 1 shows a display apparatus of a point light source system disclosed in U.S. Pat. No. 2,679,176. A light beam illuminated from a point light source 41 to traverse a convex lens 42 is refracted by the convex lens 42 and converged at a point corresponding to a light converging point 43. If an eye is at the site of the light converging point 43, the convex lens 42 in its entirety shines brightly so as to serve as a back light for a liquid crystal display screen 44 placed in a near-by position.
FIG. 2 is a plan view for a case where the point light source 41 is replaced by a light source for a right eye. In such case, the light beam emitted from a light source for the right eye 45 acts as if it is of the same component as the light beam emitted from the point light source 41 and lights the entire surface of the convex lens 42 to then fall on a right eye 46. The spatial light source by the light source 45 for the right eye causes a light source image area for a right eye 48 to be presented ahead of the convex lens 42. As long as the viewer""s right eye is at this light source image area for a right eye 48, the convex lens 42 is lighted brightly uniformly so as to serve as a back light for the liquid crystal display screen 44 placed thereat. If this is applied to left and right eyes, the light source image areas, optimized for a right eye 46 and a left eye 50, that is a light source image area for a right eye 48 and a light source image area for a left eye 49, by two light sources arranged with a center axis C of the convex lens 42 as the boundary, that is a by surface light source 45 for the right eye and by a surface light source 47 for the left eye, are formed, as shown in FIG. 3.
FIGS. 4 and 5 schematically show the state in which the light emitted from the light source 45 for the right eye and by the light source 47 for the left eye, operating as back lights, is sorted by a line-based polarization filter 52 to fall on the right eye 46 and on the left eye 50. In this case, the light illuminated from the surface light source 47 for the left eye having a leftward descending Brewster angle is first directed to the left eye 50 due to the directivity of a Fresnel lens 51. Then, only the image information for the left eye of an even line 54, having a coincident Brewster angle, falls on the left eye 50 by the line-based polarization filter 52. The light illuminated from the surface light source 45 for the right eye having a rightward descending Brewster angle is first directed to the left eye 50 due to the directivity of the Fresnel lens 51. Then, only the image information for the right eye of an odd line 53, having a coincident Brewster angle, falls on the right eye 46 by the line-based polarization filter 52.
So, the left and right parallax information, represented on the lines of the liquid crystal display screen 44, corresponding to the even line 54 and the odd line 53, fall on both eyes of a viewer 13 lying before the liquid crystal display screen 44 to become fused in the user""s brain so as to be perceived as a stereo image.
In this case, however, there is presented a problem that, since the left and right parallax information are split at a center axis C, that is at the center of the screen, the same image is incident on both eyes if the viewer 13 moves his or her head in the left and right directions, so that the both eyes enter one area, with the result that the image becomes a two-dimensional image to render the stereo vision impossible
On the other hand, if a 3D display apparatus is formed by a liquid crystal display device made up of polarizing filters 55, 56, glass substrates 57, 58, a half-wave plate 59, a color filter 60, a liquid crystal display screen 61, a protective film 62 and a transparent electrode 63, that is in a system in which the polarizing filter 56 is formed on the glass substrate 58 on the light incident side of the surface light source, the image information on a line which inherently should not be visible is superposed as crosstalk on he inherent image information if the line of sight of the viewer 13 is in the direction indicated by a dotted line arrow in FIG. 6, thus producing a stereo image extremely difficult to view.
That is, if the viewer 13 raises or lowers his or her head, the light transmitted through the half-wave plate 59 of a preset line falls astride two lines of a color filter 60 and a liquid crystal display surface 61, without coinciding with a line of the color filter 60 and the liquid crystal display surface 61 associated with this line. For example, the light which should fall on the right eye 46 also falls on the line for left eye of the color filter 60 and the liquid crystal display surface 61 to get to the left eye 50 to produce the crosstalk.
It should be noted that, since the vertical pitch of a 10.4-inch SVGA (600 by 800 pixels) is 0.264 mm, the light beam traversing a polarizing filter on a glass substrate 1 mm in thickness, if deviated xc2x115 degrees in the vertical direction, becomes wholly the illumination for the adjacent line, so that a stereo image having the convex and concave relation inverted is viewed. Even if the angle of offsetting is less than xc2x115 degrees, the degree of freedom in the vertical direction is well-nigh lost due to crosstalk. Thus, in the absence of the compensation for the difference in the seated height or in the elevation angle of the liquid crystal display surface, more constraint than that experienced in the left and right direction is imposed.
For coping with this inconvenience, a variety of techniques have been proposed which detect the head position of the viewer 13 to control an area allowing for stereo vision in accordance with detected results. For example, as methods for detecting the viewer""s head position, there are known such a method consisting in loading a magnetic sensor on the head and such a method consisting in using a video camera to detect the head image. However, with these methods, the viewer 13 may feel that a foreign object set on his or her head is cumbersome, or the cost of the product is raised. So, there has as yet not been introduced a handy 3D liquid crystal display apparatus in which the viewer 13 is able to enjoy an optimum stereo image when he or she simply sits before a liquid crystal display surface, even though he or she moves his or her head slightly in the vertical and/or left and right directions.
In view of the above-described status of the art, it is an object of the present invention to provide a liquid crystal display apparatus, liquid crystal device and liquid crystal display system in which a stereo image is not impaired and hence a high precision stereo image can be enjoyed even if the viewing position of the viewer is deviated slightly in the vertical and/or left and right directions with respect to the liquid crystal display surface.
For accomplishing the above object, the present invention provides a liquid crystal display apparatus including a liquid crystal display device having light modulating means, a first polarizing filter, arranged on the front surface of the light modulating means and a second polarizing filter arranged on the back side of the light modulating means, the light modulating means including a pair of transparent electrode plates and liquid crystals sealed therein, a first light source arranged on the back side of the liquid crystal display device, the first light source having a polarizing filter unit for the right eye and a polarizing filter unit for the left eye, the polarizing filter unit for the right eye and a polarizing filter unit for the left eye having respective different directions of polarization and being fixedly mounted on left and right portions on a front surface thereof, optical means arranged on the back side of the liquid crystal display device for collecting the illuminating light from the light source for illuminating the so-collected light on the liquid crystal display device, a second light source arranged on the front side of the liquid crystal display device for illuminating the light on the head of a viewer, light receiving devices arranged on the front sides of the polarizing filter unit for the right eye and the polarizing filter unit for the left eye at a preset spacing therefrom, and position control means for processing and comparing the volumes of the received light in the light receiving devices to control the position of the first light source in the left-and-right direction. The image information for the right eye and that for the left eye are alternately displayed on the light modulating means every horizontal line in agreement with light transmitting lines in the first and second polarizing filters, the light illuminated from the first light source through the polarizing filter unit for the right eye is incident on the right eye of the user through the liquid crystal display device, the light illuminated from the first light source through the polarizing filter unit for the left eye is incident on the left eye of the user through the liquid crystal display device, independently of the light from the first light source through the polarizing filter unit for the right eye. The volume of light illuminated from the second light source and reflected by the head of the user is sensed by the light receiving devices to detect the movement in the left-and-right direction of the head of the viewer. The position control means causes automatic movement of the position of the first light source in the left-and-right direction in agreement with the detected movement.
That is, in the liquid crystal display apparatus, according to the present invention, the light from the polarizing filter for the right eye is transmitted only through every other line on which an image for the right eye is projected to fall on the right eye of the viewer, whilst the light from the polarizing filter for the left eye is transmitted only through every other line on which an image for the left eye is projected to fall on the left eye of the viewer, so that a stereo image may be viewed due to three-dimensional perception derived from the parallax between the two eyes. So, a regular stereo image may be viewed within the ranges of the stereo vison areas of the left and right eyes.
The light illuminated from the second light source and reflected by the viewer""s head is perceived by the light receiving device to sense the movement in the left-and-right direction of the viewer""s head to cause the first light source position to be automatically shifted in the left-and-right direction in keeping with the movements of the viewer""s head.
Since the light receiving device is fixedly mounted on the first light source, the light receiving device is moved with movement of the first light source. The movement of the first light source ceases when the light receiving device gets to the preset position. Thus, even if the viewer""s head is moved in the left-and-right direction, the viewer head position is automatically tracked to cause the stereo vision area to be moved to a proper position for appreciating the stereo vision image.
On every other horizontal line of the light modulating means, the image for the right eye and that for the left eye are projected. So, the totality of the images for the right and left eyes are directly incident selectively on the right and left eyes of the viewer, thus not detracting from the horizontal resolution.
The present invention also provides a liquid crystal display device including first image separating means for separating the light illuminated from a light source depending on the direction of polarization, light modulation means having liquid crystals sealed within a pair of transparent electrode plates, the light modulation means modulating the intensity of light transmitted through the first image separating means, second image separating means for separating the light transmitted through the light modulating means depending on the direction of polarization, and a pair of substrates for clamping at least the first image separating means and the modulating means.
That is, in the liquid crystal display device according to the present invention, in which the first image separating means is arranged next to the light modulating means, the distance between the first image separating means and the light modulation means becomes shorter. The result is that the image information on a line which inherently should not be visible due to the distance between the first image separating means and the light modulation means may be prevented from entering the eye as cross-talk in superimposition on the inherent image information.
The present invention also provides a liquid crystal display system employing two, namely left and right, polarizing filters having respective different directions of polarization, including a liquid crystal display device, the liquid crystal display device including, in turn, first image separating means for separating the light illuminated from a light source depending on the direction of polarization, light modulation means having liquid crystals sealed within a pair of transparent electrode plates, the light modulation means modulating the intensity of light transmitted through the first image separating means, second image separating means for separating the light transmitted through the light modulating means depending on the direction of polarization, and a pair of substrates for clamping at least the first image separating means and the modulating means.
That is, with the liquid crystal display system according to the present invention, in which the first image separating means is arranged next to the light modulating means, the distance between the first image separating means and the light modulation means becomes shorter. The result is that the image information on a line which inherently should not be visible due to the distance between the first image separating means and the light modulation means may be prevented from entering the eye as cross-talk in superimposition on the inherent image information.
Other objects and specific advantages of the present invention will become more apparent from reading the following description of the preferred embodiments thereof when read in conjunction with the drawings and the claims.